title: Estimation of intracranial failure risk following hippocampal-sparing whole brain radiotherapy.
abstract: OBJECTIVE
  To estimate the risk of undertreatment in hippocampal-sparing whole brain radiotherapy (HS-WBRT).
  
  
  METHODS
  Eight hundred and fifty six metastases were contoured together with the hippocampi in cranial MRIs of 100 patients. For each metastasis, the distance to the closest hippocampus was calculated. Treatment plans for 10 patients were calculated and linear dose profiles were established. For SCLC and NSCLC, dose-response curves were created based on data from studies on prophylactic cranial irradiation, allowing estimating the risk for intracranial failure.
  
  
  RESULTS
  Only 0.4% of metastases were located inside a hippocampus in 3% of all patients. SCLC showed a relatively high rate of hippocampal metastasis (18.2% of all SCLC patients) and HS-WBRT in a commonly applied fractionation scheme would increase the risk for brain relapse by ∼4% compared to conventional WBRT. NSCLC showed a lower rate of brain metastasis in the hippocampi (2.8%) and HS-WBRT would account for a slightly increased absolute risk of 0.2%.
  
  
  CONCLUSIONS
  Prophylactic or therapeutic HS-WBRT is expected to be associated with a low risk of undertreatment. For SCLC, it bears a minimally elevated risk of failure compared to standard WBRT. In NSCLC, HS-WBRT is most likely not associated with a clinically relevant increase in risk of failure.
authors.affiliation: Department of Radiation Oncology.
authors.forename: Saskia
authors.initials: S
authors.lastname: Harth
authors.forename: Yasser
authors.initials: Y
authors.lastname: Abo-Madyan
authors.forename: Lei
authors.initials: L
authors.lastname: Zheng
authors.forename: Kerstin
authors.initials: K
authors.lastname: Siebenlist
authors.forename: Carsten
authors.initials: C
authors.lastname: Herskind
authors.forename: Frederik
authors.initials: F
authors.lastname: Wenz
authors.forename: Frank A
authors.initials: FA
authors.lastname: Giordano
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001932:Brain Neoplasms / Q000532:radiotherapy* / Q000556:secondary*; D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology; D018288:Carcinoma, Small Cell / Q000473:pathology; D016371:Cranial Irradiation; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006624:Hippocampus / Q000473:pathology / Q000528:radiation effects*; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology; D008297:Male; D008875:Middle Aged; D011880:Radiotherapy Planning, Computer-Assisted; D012189:Retrospective Studies; D012306:Risk
keywords: Brain metastasis; Hippocampal-sparing whole brain radiotherapy; Prophylactic cranial irradiation; Whole brain radiotherapy